APC backup beeps when printer is on

Using XP, APC Back-UPS ES-350 and Brother HL-1440 laser printer.

Not sure this has a viable solution, but will ask anyway.

My backup power supply beeps when ever the printer is on. I get 4 beeps every minute or so, all day. Initially, I thought the printer was beeping, since I only heard the beeps when the printer was on. Went to the Brother website and Brother indicated that its printer is not able to beep. Narrowed the beeping sound to the backup power supply.

The printer was plugged into the backup power supply and whenever the printer was on, I would get the 4 beeps every minute or so. Removed the printer connection from the backup power supply and connected the printer to a wall jack, for power, and it still beeps. The only way to get rid of the beeping is to turn the printer off. I now turn the printer on to print and turn it off when the printing is finished.

Both the printer and the backup power supply are connected to the same circuit breaker for my household current, and I cannot change that.

Why in the heck is my backup power supply beeping, again only when the printer is on, and is there any way to resolve this problem?